Shader "Study/Chapter4/Alpha Blend ZWrite"
{
    Properties
    {
        _MainTex ("Main Tex", 2D) = "white" {}
		_AlphaScale ("Alpha Scale", Range(0, 1)) = 1
		_Color ("Color Tint", Color) = (1, 1, 1, 1)
		[Enum(UnityEngine.Rendering.BlendMode)]_SrcFactor("SrcFactor ",int) = 0
        [Enum(UnityEngine.Rendering.BlendMode)]_DstFactor("DstFactor ",int) = 0
		
    }
    SubShader
    {
        Tags {"Queue"="Transparent" "RenderType"="Transparent" }

		Pass
		{
			// 仅为了写入模型的深度信息
			ZWrite On
			ColorMask 0
		}

        Pass
        {
			Tags { "LightMode"="ForwardBase" }

			ZWrite Off
       		//Blend SrcAlpha OneMinusSrcAlpha
			Blend [_SrcFactor] [_DstFactor]

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

			fixed4 _Color;
            sampler2D _MainTex;
            float4 _MainTex_ST;
			fixed _AlphaScale;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
				col.rgb = col.rgb * _Color.rgb;
				// 通过面板参数，控制透明度
                return fixed4(col.rgb,col.a * _AlphaScale);
            }
            ENDCG
        }
    }
}
